Photography – With film drive – Film movement limiting means
Reexamination Certificate
1999-11-19
2001-07-17
Perkey, W. B. (Department: 2851)
Photography
With film drive
Film movement limiting means
C396S406000
Reexamination Certificate
active
06263169
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improvement on a manual-wind camera provided with a wind lever which is manually operated to wind the film frame by frame.
2. Description of the Related Art
Manual-wind cameras having a film winding mechanism provided with a wind lever (i.e., thumb-operated lever) which is manually operated to wind the film frame by frame are known in the art.
Conventional cameras of such a type are provided with a pulse generator which generates pulses in accordance with the film winding via the operation of the wind lever. Pulses generated by the pulse generator are counted by a counter to release the engagement of the wind lever with the take-up spool at the moment the counted number of the counter becomes identical to a reference pulse number which corresponds to a predetermined appropriate film-winding amount, so that the film is wound by the appropriate film-winding amount each time the film is wound by one frame.
In conventional manual-wind cameras using a roll-film having no sprocket holes such as Brownie film (e.g., 120 or 220 format film), turning the wind lever slowly makes the film winding speed slow while turning the wind lever quickly makes the film winding speed fast. However, the amount of operation of the wind lever does not exactly correspond to the amount of winding of the film because the film slips on the film guide roller, the amount of rotation thereof corresponding to the number of pulses generated by the aforementioned pulse generator, especially when the film is wound at a fast speed, i.e., when the wind lever is turned quickly. Accordingly, the amount of winding of the film by one frame varies slightly depending on the film winding speed. Furthermore, if the film winding speed is fast, even if the engagement of the wind lever and the spool is released, until they are actually released, the film can wind faster than the low film wind speed, or due to momentum, the spool does not stop immediately and winds on a little further. Even if the spool is lock-engaged when the film has finished winding, so that the film is stopped from being wound, the film can wind faster than the low film wind speed and be wound substantially more than a predetermined amount until the spool has actually been lock-engaged. If the amount of winding of the film by one frame is excessive, one or more exposures of the roll-film may be lost (e.g., the last exposure on the film may be lost), resulting in a substantial financial loss since roll-film having no sprocket holes such as Brownie film is usually expensive as compared with conventional 35 mm film.
SUMMARY OF THE INVENTION
The primary object of the present invention is to provide a manual-wind camera using a roll-film having no sprocket holes, wherein the amount of winding of the film by one frame can be made constant regardless of the speed of rotation of the wind lever.
To achieve the object mentioned above, according to an aspect of the present invention, a manual-wind camera is provided having a wind lever in which a film having no sprocket holes is loaded, the film being wound on a take-up spool, frame by frame, by manually operating the wind lever. The camera includes a pulse generator which generates pulses in accordance with movement of the film wound by the wind lever, and a counter which detects and counts the pulses generated by the pulse generator, the pulse generator and the counter are connected to a control device. The control device detects a film winding speed of the film in accordance with the number of the pulses counted by the counter, wherein the control device adjusts a reference pulse number, which corresponds to a predetermined appropriate winding amount of the film, in accordance with a the film winding speed detected by the control device. An engagement of the wind lever with the take-up spool is released at the moment the adjusted reference pulse number becomes equal to the number of the pulses counted by the counter.
Preferably, the counter includes a down counter which is firstly set to the reference pulse number and which decreases the counter value of the down counter by one, each time the counter detects a pulse generated by the pulse generator.
Preferably, the control device sets the counter value of the down counter to the number of remaining pulses which is obtained by subtracting the current number of pulses counted by the counter from the adjusted reference pulse number.
Preferably, an engagement of the wind lever with the take-up spool is released at the moment the counter value of the down counter becomes zero.
Preferably, the control device calculates an adjustment amount in accordance with the film winding speed to adjust the reference pulse number in accordance with the calculated adjustment amount if the film winding speed detected is within a predetermined range.
Preferably, a plurality of film-pulse-speed adjustment algorithms is provided; wherein one of the plurality of film-pulse-speed adjustment algorithms is selected by the control device in accordance with the detected film winding speed.
Preferably, the control device adjusts the primary reference pulse number by subtracting a fixed pulse number, as a maximum adjustment pulse number, from the primary reference pulse number if the film winding speed exceeds a predetermined film winding speed which is fastest among a plurality of predetermined film winding speeds determined within the predetermined range.
Preferably, upon the control device adjusting the primary reference pulse number, if the film wind speed changes to a speed lower than the predetermined film winding speed, the calculated adjustment amount is subtracted from the primary reference pulse number, wherein the value of the adjusted pulse returns to the primary reference pulse number, so that the primary reference pulse number is not adjusted.
Preferably, a counter is further included, which counts an amount of winding of the film, wherein the control device starts detecting the film winding speed after the film is wound by a half frame.
Preferably, a film guide roller is further included, which is rotated in accordance with the movement of the film, wherein the pulse generator includes a photo-interrupter and an associated rotary disc having a plurality of radial slits, the rotary disc being coaxially secured to an end of the film guide roller.
Preferably, the film is Brownie film.
The present disclosure relates to subject matter contained in Japanese Patent Application No.10-329744 (filed on Nov. 19, 1998) which is expressly incorporated herein by reference in its entirety.
REFERENCES:
patent: 5655169 (1997-08-01), Newman
patent: 5708887 (1998-01-01), Funaki et al.
patent: 5903784 (1999-05-01), Hori
patent: 6026250 (2000-02-01), Goto et al.
patent: 0676665 (1995-10-01), None
Asahi Kogaku Kogyo Kabushiki Kaisha
Greenblum & Bernstein P.L.C.
Perkey W. B.
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